Coupling device of magnetic particle type

ABSTRACT

A magnetic-particle-type coupling device for transmitting the rotation of an engine to a transmission. One end portion of a heat pipe is embedded in a driven body, the other end portion of the heat pipe is inserted in the internal opening of the input shaft of the transmission, and cooling oil is supplied into the internal opening, so that the driven body and a driving body are efficiently cooled although the coupling device is made compact.

TECHNICAL FIELD

The present invention relates to a magnetic-particle-type couplingdevice for transmitting the rotation of the crankshaft of an engine to atransmission, and particularly relates to the improvement of a means forcooling the driven body of the coupling device.

BACKGROUND ART

FIG. 1 shows a conventional magnetic-particle-type coupling devicedisclosed in the Japanese Patent Application (OPI) No. 60733/81 (theterm "OPI" as used herein means an "unexamined published application").Rotation whose speed is changed by a transmission 2 to which thecoupling device 1 is connected is decelerated by the differential gearunit of a speed reducer 3 and then transmitted to axles. Themagnetic-particle-type coupling device 1 comprises a driving body 4constructed by conjoining two members to each other in the axialdirection of the coupling device and secured to a driving plate 6secured to a crankshaft 5; an excitation coil 7 housed in the opening ofthe driving body 4; a driven body 8 whose outside circumferentialsurface faces the inside circumferential surface of the driving body 4across a gap and which is secured to a hub 11 supported by a bearing 10to a bracket 9 attached to the driving body; magnetic particles 12filled in the gap; a pair of slip rings 13 which are secured with anelectric insulation bushing 15 to a cap 14 attached to the bracket 9 andare connected so as to supply electricity to the excitation coil 7; abrush unit 16 for supplying the electricity through the slip rings 13;and a coupling shaft 17 secured to the hub 11 and constituting the inputshaft 17a of the transmission 2. A case 18 houses the coupling device 1and the transmission 2. A temperature sensor 19 is secured to theportion of the case 18, which faces the coupling device 1. Shown at 20and 21 in FIG. 1 are a ring gear and the output shaft of thetransmission 2, respectively.

When the electricity is supplied to the excitation coil 7 as the drivingbody 4 is rotated by the crankshaft 5 after the starting of an engine,the magnetic particles 12 are magnetized to couple the driving body andthe driven body 8 to each other to transmit the rotation of the drivingbody to the driven body to rotate the input shaft 17a of thetransmission 2 through the coupling shaft 17. Between the input shaft17a and output shaft 21 of the transmission 2, the speed of the rotationis changed among a low, a second, a third and a fourth speed stages by aplurality of speed change gear means between the input and the outputshafts in response to the manipulation of a manual speed change lever.The rotation of the output shaft 21 is transmitted to wheels through thedifferential gear unit of the speed reducer 3 and the axles.

Since it is necessary to smoothly increase the coupling torque of themagnetic-particle-type coupling device 1 at the time of starting of avehicle, a slip takes place between coupling members to generate heat toraise the temperature of the coupling device. If the rise in thetemperature of the coupling device is large, the device burns. This is aproblem.

To prevent the problem, the temperature sensor 19 is attached to thecase 18 to supply a signal from the temperature sensor to a controllerthrough a second speed stage switch which is turned on when the vehicleis started at the second speed stage of the transmission 2. When thesecond speed stage switch is turned on and the temperature in the case18 has exceeded a limit due to the frequent repetition of the startingof the vehicle at the second speed stage of the transmission 2, thesignal from the temperature sensor 19 is supplied to the controller toalter the electrical current of a clutch to shift the torque of theclutch to a level for a lower speed stage. As a result, the starting ofthe vehicle at the second speed stage of the transmission 2 is madeimpossible to suppress the rise in the temperature in the case 18 toprevent the coupling device 1 from burning.

However, since the temperature of the internal opening of the case 18 isdetected by the temperature sensor 19, it is difficult to accuratelydetect the temperature of the driving body 4 or the driven body 8.Particularly when the temperature of the driving body 4 or the drivenbody 8 has exceeded a limit in a short time, the detection of the risein the temperature by the temperature sensor 8 delays so that thecoupling device 1 burns. This is another problem. Although it ispossible to attach cooling fins or the like to the driving body 4 in anouter position to cool the driving body, it is difficult to cool thedriven body 8 in an inner position. This is still another problem.

A conventional cooler for a magnetic-particle-type coupling device wasdisclosed in the Japanese Utility Model Application No. 510/85. In thecooler circumferential surface of a stator in an internal position issecured to the hermetically sealed tube of a heat exchanger, coolingfins are provided on the outer end portion of the tube and project intothe external air, a wick is provided in the tube, and a working liquidis hermetically enclosed in the tube. Although the stator in theinternal position can be cooled by the external air through the heatexchanger of the cooler, the efficiency of heat transfer by a means fortransferring the heat of the stator to the external air through thecooling fins of the heat exchanger is low and the cooling fins need alarge heat transfer area which means that the installation space for thecooler is large. These are still other problems.

The present invention was made in order to solve the above-mentionedproblems.

Accordingly, it is an object of the present invention to provide amagnetic-particle-type compact coupling device in which a driven body isdirectly cooled through efficient transfer of heat to enable thecoupling device to withstand severe operation.

DISCLOSURE OF THE INVENTION

In the magnetic-particle-type coupling device provided in accordancewith the present invention, the heat-incoming portion of a heat pipe isembedded in the driven body and the heat-outgoing portion of the heatpipe is inserted in the hole of the input shaft of a transmission so asto be cooled by cooling oil supplied into the hole.

Since the heat-outgoing portion of the heat pipe is efficiently cooledby the cooling oil of high thermal conductivity, the driven body isdirectly cooled so that the driving body of the coupling device isindirectly cooled. As a result, the temperature of the coupling deviceis prevented from excessively rising. Besides, the size of the couplingdevice is not increased.

BRIEF DESCRIPTION DRAWINGS

FIG. 1 shows a sectional view of a conventional magnetic-particle-typecoupling device.

FIG. 2 shows a sectional view of a magnetic-particle-type couplingdevice which is an embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is hereafter described with reference to thedrawings so as to be understood in detail. FIG. 2 shows amagnetic-particle-type coupling device which is an embodiment of thepresent invention and connected to a transmission. The mutuallycorresponding portions shown in FIGS. 1 and 2 are denoted by the samereference symbols therein.

As shown in FIG. 2, the input shaft 30 of the transmission 2 isspline-connected to the splined portion 17b of a coupling shaft 17 andhas an internal opening 30a extending along the axis of the input shaftand has a through hole 30b through which the internal openingcommunicates with an opening around the outside circumferential surfaceof the input shaft near the coupling shaft. A working liquid, which isrepeatedly evaporated and liquefied, and a wick for moving the workingliquid are hermetically enclosed in a heat pipe 31 whose heat-incomingend portion 31a is radially ramified in the radial direction of thecoupling device 1 and embedded in a driven body 8 and whoseheat-outgoing end portion 31b extends in the coupling shaft 17 along theaxis thereof and projects into the internal opening 30a of the inputshaft 30. The output shaft 32 of the transmission 2 has an internalopening 32a extending along the axis of the output shaft, and aplurality of through holes 32b through which the internal openingcommunicates with an opening around the outside circumferential surfaceof the output shaft. The internal openings 30a and 32a and the throughholes 30b and 32b constitute passages through which cooling oil iscirculated.

When an excitation coil 7 is supplied with electricity after thestarting of an engine, magnetic particles 12 are magnetized so that adriving body 4 and the driven body 8 are coupled to each other. Althoughheat is generated due to a slip between the driving body 4 and thedriven body 8 so that the temperature of the driving and the drivenbodies rises, some of the heat is transferred from the peripheralsurfaces of the driving and the driven bodies and the other of the heatis conducted to the heat-incoming end portion 31a of the heat pipe 31 sothat the working liquid supplied into the heat-incoming end portionthrough the wick is sequentially evaporated by the conducted heat. Inthe meantime, the cooling oil is supplied into the internal opening 30aof the input shaft 30 in a direction A from outside by an oil pump(which is not shown in the drawing) to cool the heat-outgoing endportion 31b of the heat pipe 31 to liquefy the vapor of the workingliquid. For that reason, the heat of the driven body 8 is taken out bythe cooling oil. The driving body 4 is also cooled as the temperature ofthe driven body 8 is lowered.

After the cooling oil supplied into the internal opening 30a of theinput shaft 30 cools the heat pipe 31, the cooling oil flows through thethrough hole 30b and lubricates the gears of the transmission 2 and isthereafter returned to an oil tank (which is not shown in the drawing)through the through holes 32b and internal opening 32a of the outputshaft 32. As a result, the transfer of the heat from the heat pipe 31 isefficiently performed by the cooling oil. Since it is not necessary toprovide cooling fins or the like to perform the transfer of the heat,the coupling device 1 can be made compact.

Although the excitation coil 7 is housed in the driving body 4 in theabove-described embodiment, the present invention is not confinedthereto but may be otherwise embodied so that the driven body 8 is madeof two portions split from each other in the axial direction of thedriven body and the excitation coil is housed therein.

According to the present invention, the heat-incoming portion of theheat pipe is embedded in the driven body and the heat-outgoing portionof the heat pipe is inserted in the oil hole of the input shaft of thetransmission so as to be cooled by the cooling oil, as described above,as a result, the generated heat is efficiently removed to suppress therise in the temperature of the driving and the driven bodies to enablethe magnetic-particle-type coupling device to withstand severeoperation. Besides, the coupling device is compact.

I claim:
 1. A magnetic-particle-type coupling device for transmittingthe rotation of a crankshaft of an engine to an input shaft of atransmission, said input shaft having an axial internal opening, saidcoupling device comprising:an annularly-shaped driving body having aninside circumferential surface; a driven body whose outsidecircumferential surface faces the inside circumferential surface of saiddriving body with a gap therebetween, said driven body being coupled tosaid input shaft; magnetic particles disposed in said gap; an excitationcoil circumscribing said driven body for magnetizing said particles tocontrol the state of connection of said driving and driven bodies; andan elongate heat pipe having one end thereof embedded in said drivenbody and another end of said pipe inserted in the internal opening ofsaid input shaft, wherein cooling oil is supplied into said internalopening to cool said other end of said pipe, and wherein said one end ofthe heat pipe is radically ramified in the radial direction of thedriven body.
 2. A magnetic-particle-type coupling device according toclaim 1, wherein a coupling shaft is provided in the driven body alongthe axis thereof; the input shaft of the transmission is spline-coupledto said coupling shaft; and the heat pipe is inserted into the internalopening of said input shaft through said coupling shaft along the axisthereof.
 3. A magnetic-particle-type coupling device for transmittingthe rotation of a crankshaft of an engine to an input shaft of atransmission, said input shaft having an axial internal opening, saidcoupling device comprising:an annularly-shaped driving body having aninside circumferential surface; a driven body whose outsidecircumferential surface faces the inside circumferential surface of saiddriving body with a gap therebetween, said driven body being coupled tosaid input shaft; magnetic particles disposed in said gap; an excitationcoil circumscribing said driven body for magnetizing said particles tocontrol the state of connection of said driving and driven bodies; andan elongate heat pipe having one end thereof embedded in said drivenbody and another end of said pipe inserted in the internal opening ofsaid input shaft, wherein cooling oil is supplied into said internalopening to cool said other end of said pipe, and wherein said inputshaft of the transmission has the internal opening extending along theaxis of said input shaft, and a through hole through which said internalopening communicates with an opening around an outside circumferentialsurface of said input shaft the cooling oil being drained through saidthrough hole.